Snap action switch



Jan. 18, 1955 A. w. HAYDON SNAP ACTION SWITCH Filed Sept. 16, 1950 FIG.

FIG. 2

United States Patentt) SNAP ACTION SWITCH Arthur W. Haydon, Cheshire, Conn., assiguor to Haydon Switch, Incorporated, Waterbury, Conn., a corporation of Connecticut Application September 16, 1950, Serial No. 185,247

20 Claims. (Cl. 200-67) This invention relates to electric switches and more particularly is concerned with a novel switch of the type commonly known in the trade as snap action switches. Such switches are so-called becauseof their quick make-and-break action.

As a result of a comprehensive survey of snap action switches now in commercial use with a view to finding one which might be operated by a slow moving cam, I have found none which can be so operated satisfactorily. Without exception, all snap action switches with which I am familiar suifer the same handicap, which is that as operating pressure is progressively applied to them through their actuating means, the contact pressure between their spring blades and contacts progressively decreases until finally the blade snaps and the switch circuit is broken. When the operating pressure is applied to the actuating means by a cam, which may do so very slowly, such a decrease in pressure between the contacts and the spring blades cannot be tolerated if the current passing through the switch circuit is to remain normal and constant until the circuit is broken.

For instance, one use for a snap action switch which I contemplate is in a timer, wherein the switch is to be operated by a cam supported on a cam shaft which is revolved at speeds of as little as one revolution per day. In such a device the switch is called upon to carry normal current for a considerable lengthv of time during the latter portion of the movement of the switch actuating means. In order to accomplish thisthe pressure between the switch contacts or, more accurately between the spring blade of the switch and a switch contact, must be at least as great as it normally is, when no operating pressure is being applied to the actuating means, right up to the time at which the switch blade snaps to break the circuit. In none of the switches in commercial use with which I am familiar is the contact pressure so maintained.

It is, therefore, the primary object of my invention to provide a snap action switch in which the contact pressure of the switch is kept relatively large substantially throughout the movement of the switch actuating means. As a matter of fact, in the switch contemplated by this invention the contact pressure is progressively increased as the switch actuating means is progressively moved towards its final position at which the switch operates. Incidental to the attainment of this object, the design of the snap action switch contemplated by this invention is such that numerous other advantages are realized.

Broadly, my invention contemplates a snap action switch in which the novelty of the design of the spring blade member is primarily responsible for the maintenance of good contact pressure substantially to the point at which the switch circuit is broken. This spring blade is generally rectangular in shape and has a pair of substantially longitudinally extending slots formed in it. The portions of the bladeon the outer sides of the slots are crimped to shorten effectively the length of the blade and the portion of the blade between the slots is bent or deformed to form an arch out of the plane of the blade. The deformation of the central portion of the blade is controlled so that the peak of the arch is off-set to one side of its longitudinal mid-point.

More specifically the snap action switch contemplated by this invention comprises a base member of insulating material in which are supported a pair of substantially L-shaped terminals one arm of each of which extends through the base member, the other arm extending sub- 2,700,079 Patented Jan. 18, 1955 2 stantially parallel to the base member. The spring blade above described is adapted to be supported by one of the L-shaped terminals at its end adjacent the peak of the arch, the other end of the bladenormally engaging the unsupported arm of the other L-shaped terminal. A switch actuating member is also adapted to be supported by the blade-supporting L-shaped terminal and engages the peak of the arch of the blade when moved toward its switch operating position. The ends of the arms of the L-shaped terminals which extend from the face of the base member opposite that on which the spring blade is supported, will be provided with holes there-through by which plain soldered connections with lead wires may be readily made.

The invention also contemplates the provision of screw terminals for the connection of lead wires. To this end, an L-shaped screw terminal member is provided for each of the L-shaped terminals. Such a screw terminal member is adapted to have one end secured in the. hole in the end of the L-shaped terminal and its other end extending into a recess in the base member. A screw is threaded through one arm of the L-shaped screw terminal member. By reason of this construction the switches may be standardized and yet, by simple modifications may be made to accommodate the requirement of screw terminals or plain soldered terminals, whichever are necessary.

For a more detailed description of one form of my novel snap action switch reference may be made to the accompanying drawing in which:

Fig. 1 is a plan view of the switch;

F Fig. 2 is a sectional view thereof on line 22 of Fig. 3 is another sectional view of the switch on line 3-3 of Fig. 2; and

Fig. 4 is a perspective view of the spring blade of the switch.

By reference to the drawings, the switch comprises a base member 10 of any suitable insulating material though it is contemplated that Bakelite will be used. Three substantially L-shaped terminal members'll, 12 and 13 are mounted in openings 14, 15 and 16, respectively, through the base member. The arms of terminal members 11, 12 and 13 which extend through the openings in the base member are substantially identical, each having shoulders 17 (see Fig. 3) which engage the upper face of the base member 10 and a reduced portion 18 extending below the base member and through which there is formed an opening 19 whereby a lead wire (not shown) may be soldered thereto.

Should it be necessary to provide a switch with screw terminals rather than plain soldered terminals, screw terminals 20, 21 and 22 may be provided respectively for terminal members 11, 12 and 13. Such screw terminals 20, 21 and 22 comprise L-shaped members having at one end tongues 23 which are adapted to pass through openings 19 in terminal members 11, 12 and 13 and to be secured thereto by riveting. The other ends of the screw terminals are adapted to enter recesses 24 formed in the base member. A screw 25 is threaded through the arm of each screw terminal which is substantially parallel to the base member 10. By means of screws 25, lead wires may be secured to the screw terminals. It will be noted that openings 19 in terminal members 11, 12 and 13 are located inwardly from the ends thereof whereby a portion 26 of each terminal member extends beyond the screw carrying arm of the screw terminals. Portions 26 thereby serve to hold lead wires under the head of the screws which is necessary to meet Underwriter requirements.

In view of the above described terminal construction, the switches may be standardized, yet by simple modification may be made to accommodate the requirement 'for either plain soldered terminals or screw terminals.

supported by having one end secured, by a rivet 31, to the unsupported arm of terminal member 11 between then nsupported arm and a blade adjusting member 32 the function of which will be subsequently described. The unsupported end of the spring blade extends between the unsupported arm and a blade adjusting member 32 and is provided with pure silver contacts 33, which are adapted to alternately engage coil silver inlays 34 and 35 in the unsupported arms of terminals 12 and 13.

The design of spring blade 30 may best be seen in the perspective view shown in Fig. 4. The blade comprises a substantially rectangular strip of spring material, preferably beryllium copper, having a pair of substantially longitudinal slots 36 formed in it. The portions of the blade on the outer sides of slots 36, which may be termed tension members or portions of the blade, are crimped as at 37 to shorten eficctively the length of the blade and to deform the central portion of the blade between the slots into an arch 38. The deformation of the central portion or arch 38 of the blade, which may be termed the compression member or portion of the blade, is carefully controlled so that the peak of the arch is offset from the longitudinal mid-point of the arch in the direction of the supported end of the blade.

Returning to Fig. 2, a switch actuating member 39 is provided which is secured to terminal member 11 by means of a tongue 40 which passes through an opening 41 in the distal end of the unsupported arm thereof. In the use of my switch for which actuating member 39 is designed, the upper end 42 thereof is adapted to be engaged by a cam which progressively applies a downward pres sure therethrough to the arch of the spring blade. The actuating member has a shoulder 43 which is adapted to engage the arch 38 of the blade substantially at its peak or slightly to one side thereof in the direction of the supported end of the blade. When the actuating member has been moved downward a suflicient distance the spring blade will snap from its normal position as indicated in solid lines in Figure 2, to its thrown position, as indicated in the same figure by dotted lines.

The blade adjusting member 32, which extends beneath the supported end of blade 30, is provided for making slight adjustments in the switch to compensate for variations in production and also permits making adjustment to change the throw point of the switch slightly to control the center of motion of the spring blade in relation to the fixed contacts of terminal members 12 and 13. Hence satisfactory operation of each production switch may be possible without the necessity of holding exceedingly close tolerances in the fabrication of the various parts. For the purpose of adjusting the adjusting member and thereby the position of switch blade 3t an adjustment screw 44 is provided which is threaded through base member 16 and adapted to engage the under surface of the outer end of member 32.

My present theory as to the operation of the switch and the various changes in the condition of the spring blade 30 in changing from its normal position as shown in solid lines, to its snapped position shown in dotted lines is as follows: as the actuating member 3 is moved downwardly and shoulder 43 thereof engages and depresses the arch 38 of the blade, the peak of the arch will move forward toward the free end of the blade in a motion similar to wave propagation. Thus it seems that the single arch 38 of the blade becomes, in fact, two arches, one beneath the moving peak and the other beneath the point of contact of shoulder 43 with the blade. As the actuating member is moved downwardly still further the arch beneath it tends to decrease and that beneath the moving peak to increase until the center portion between the arches collapses thus causing the arch beneath the peak to be inverted with the resultant snap action of the switch. The arch beneath the actuating member does not invert.

This double arch effect is, I believe, at least partially responsible for maintaining the contact pressure high right up to the instant of throw. Since the second arch, that is the arch which finally inverts, is under compression and is at an angle with respect to the center line of the spring blade, it naturally produces a downward component of force on the contact. Collapsing of the arch becomes automatic and uncontrollable before a dead center relation is reached and therefore good contact pressure is maintained right up to the instant of throw. In most other snap action switches there is a dead center toggle effect which, of course, is incapable of producing 4 any such perpendicular component when it passes through dead center position, and, therefore, the contact pressure must decrease to zero prior to the snap of the switch.

In its operated position the center portion of the spring blade is in an S configuration. This configuration of the blade results in the blades giving the same snap action in the return movement thereof as in conventional switches so that it is entirely satisfactory for a ntunber of applications although the superior snap action obtained in the above described initial actuation of the switch is not obtained. The return movement of the spring blade, however, is not so important. because it is contemplated that the cam by which the switch is operated will be provided with a sharp drop whereby the actuator is permitted to snap quickly back to its initial position. Also in time delay relays in which the switch might be employed, the release mechanism operates rapidly although the actuating interval may be quite prolonged. Therefore, the switch of this invention may be applied to numerous devices to full advantage even though the superior snap action, that is the snap action of the blade when the actuator is depressed, is obtained in one direction only.

In comparative tests which I have made of the operation of my novel switch and other commonly used commercial switches, I have found that in the commercial switches, during approximately the last half of the movement of the switch actuator, the contact pressure decreases constantly from the normal to zero whereas in my switch during the same period of movement, the contact pressure is actually increased well above the normal contact pressure until at least the last 5% of movement of the actuator and then only, begins to decrease below the normal. It still, however, does not reach zero until the throw point is arrived at.

While this feature is of primary importance, those skilled in the art will recognize many additional advantageous features of my switch which may not have here been fully set forth. It will also be apparent that it may be possible to make certain modifications in the design of my switch without departing from the scope of my invention and I therefore do not desire to be limited in my invention other than to the extent set forth in the appended claims.

I claim:

1. In a snap action switch of the type described, a spring blade adapted to be supported at one end and to have its other end free to move into and out of contact with a switch contact, said spring blade having a pair of substantially parallel, longitudinally extending slots formed therein, the portion of the blade between the slots forming a substantially longitudinal arch having its peak ofi-set to one side of its longitudinal mid-point.

2. In a snap action switch of the type described, a spring blade adapted to be supported at one end and to have its other end free to move into and out of contact with a switch contact, said spring blade having a pair of substantially parallel, longitudinally extending slots formed therein, the portions of the blade on the outer sides of the slots being crimped to shorten effectively the length of the blade and the portion of the blade between the slots being bent to form an arch out of the plane of the blade, said arch having its peak off-set to one side of its longitudinal mid-point.

3. A spring blade as set forth in claim 2 in which the crimped outer portions of the blade lie on the opposite side of the plane of the blade from the arch.

4. A snap action switch as set forth in claim 2 in which the peak of the arch of the spring blade is oifset toward the support for the blade.

5. A snap action switch comprising a spring blade, a support for one end of the blade, a contact adapted to be normally engaged by the opposite end of the blade, and a blade actuating member adapted to apply actuating pressure to the blade to cause its said opposite end to move out of engagement with said contact, said spring blade having a pair of substantially longitudinally extending slots formed therein, the portion of the blade between the slots forming a substantially longitudinal arch having its peak ofif'set to one side of its longitudinal mid-point, and said blade actuating member being adapted to engage said arch of the blade substantially at the peak thereof.

6. A snap action switch comprising a spring blade, a support for one end of the blade, a contact adapted to be normally engaged by the opposite end of the blade,

and a blade actuating member adapted to apply actuating pressure to the blade to cause its said opposite end to move out of engagement with said contact, said spring blade having a pair of substantially longitudinally extending slots formed therein, the portions of the blade on the outer sides of the slots being crimped to shorten eifectively the length of the blade and the portion of the blade between the slots being bent to form an arch out of the plane of the blade, said arch having its peak off-set to the side of its longitudinal mid-point closest its supported end and said blade actuating member being adapted to engage said arch of the blade between its peak and the supported end of the blade.

7. A snap action switch comprising a spring blade, a support for one end of the blade, a contact adapted to be normally engaged by the opposite end of the blade, and a blade actuating member adapted to apply actuating pressure to the blade to cause its said opposite end to move out of engagement with said contact, said spring blade having a pair of substantially parallel, longitudinally extending slots formed and terminating therein, a portion of the blade between the slots forming a substantially longitudinal arch having its peak offset to one side or" its longitudinal mid-point, the remainder of the portion of the blade between the slots lying within the plane of the blade.

8. In a snap action switch of the type described, a base member, a pair of substantially L-shaped terminals mounted in the base member, one arm of each L-shaped terminal extending through the base member and having an opening therethrough by which a lead wire may be secured to it, a spring blade secured at one end to the unsupported arm of one L-shaped terminal and having its other end extending over the unsupported arm of the other L-shaped terminal, and a screw terminal connected to each L-shaped terminal on the opposite side of the base member from the spring blade, said screw terminal comprising a substantially L-shaped member, one arm of which is secured in the opening in the arm of an L-shaped terminal and the other end of which extends into a recess in the face of the base member, and a screw threaded into one arm of the L-shaped member.

9. In a snap action switch of the type described, a base member, first and second substantially L-shaped terminals, one arm of each of which extends through the base member and the other arms of which extend toward each other on one side of the base member, a third substantially L-shaped terminal having one arm extending through the base member and having its other arm extending on said one side of the base member toward and partially beneath the unsupported arm of said first L-shaped member, a spring blade secured to the unsupported arm of said second L-shaped terminal and extending toward and between the unsupported arms of the first and third L-shaped terminals, and a blade actuating means secured to the unsupported arm of said second L-shaped terminal.

10. A snap action switch as set forth in the claim 9 in which a screw terminal is provided for each L-shaped terminal on the opposite side of the base member from the spring blade, said screw terminal comprising an L-shaped member one end of which is secured to the end of a terminal extending from said opposite side of the base member and the other end of which extends into a recess in the base member, and a screw threaded into one of the arms of the screw terminal.

11. A snap action switch as set forth in claim 9 in which the free end of the spring blade normally engages the third L-shaped terminal, and which includes an adjusting member to adjust the position of the blade.

12. A snap action switch comprising a spring blade, a support for one end of the blade which has portions overlying and underlying said end of the blade, a contact adapted to be normally engaged by the opposite end of the blade, and a blade actuating member adapted to apply actuating pressure to the blade to cause its said opposite end to move out of engagement with said contact, said spring blade having a pair of substantially parallel, longitudinally extending slots formed and terminating therein, the portion of the blade between the slots forming a substantially longitudinal arch having its peak oifset to one side of its longitudinal midpoint, said overlying and underlying portions of said blade support extending lengthwise of the blade partially to overlie and underlie said slots and the portion of blade between the slots.

13. A snap action switch comprising a switch blade having connected longitudinally extending compression and tension members, a fixed support at one end of said blade, a pair of spaced contacts located on opposite sides of the other end of said blade, means for simultaneously applying positive pressures in opposite directions to said compression and tension members to increase the stress therein to a degree in excess of the stress present in said blade when unmounted, the said simultaneously applied pressures acting to hold said blade in a normal position where it will engage that contact I toward which the pressure on said compression member is directed, means for increasing the opposed pressure on said members whereby said tension member will be put under greater tension and said compression member will be further compressed and caused at least in part to reverse itself to move said blade from said normal position against said contact to a position against said other contact.

14. A snap action switch comprising a switch blade having connected longitudinally extending compression and tension members, a fixed support at one end of said blade, a pair of spaced contacts located on opposite sides of the other end of said blade, the compression member being arched out of the plane of the blade, means for applying positive pressures in opposite directions to said compression and tension members to increase the stress therein to a degree in excess of the stress present in said blade when unmounted, the means for applying pressure to the compression member being located to apply said pressure to the convex side of the arch of said compression member to hold said blade in a normal position where it will engage that contact toward which the pressure on said compression member is directed, the fixed support for the blade engaging said tension member at a point on the side of the blade opposite the convex side of the arch and transversely out of line with the point at which the pressure applying means for the compression member contacts the convex side of the arch thereof, said tension member being crimped to decrease the force required to elongate said member and allow the compression member to at least partially invert.

15. A snap action switch according to claim 14 in which the compression and tension members are of substantiallyequal length and the length of each is equal to at least half the length of the blade.

16. A snap action switch according to claim 14 in which a portion of the compression member lies in the plane of the blade.

17. A snap action switch according to claim 16 in which one end of the arch of the compression member having connected longitudinally extending compression and tension members, a fixed support at one end of said blade, a pair of spaced contacts located on opposite sides of the other end of said blade, the compression member being arched out of the plane of the blade, means for applying positive pressures in opposite directions to said compression and tension members to increase the stress therein to a degree in excess of the stress present in said blade when unmounted, the means for applying pressure to the compression member being located to apply said pressure to the convex side of the arch of said compression member to hold said blade in a normal position where it will engage that contact toward which the pressure on said compression member is directed, the means for applying pressure to the tension member being located to apply said pressure thereto at a point on the side of the blade opposite the convex side of the arch and transversely out of line with the point at which the pressure applying means for the compression member contacts the convex side of the arch thereof, said tension member being crimped to decrease the force required to elongate said member and allow the compression member to at least partially invert.

19. In a snap action switch of the type described, a spring blade adapted to be supported at one end and to have its other end free to move into and out of contact with a switch contact, said spring blade having a pair of substantially parallel longitudinally extending slots formed therein, the portion'of the blade between the slots forming a substantially longitudinal arch extending out of the plane of the blade on one side thereof only and having its peak offset to one side of its longitudinal midpoint.

20. A snap action switch comprising a spring blade, a support for one end of the blade, a contact adapted to be normally engaged by the opposite end of the blade, and a blade actuating member adapted to apply actuating pressure to the blade to cause its said opposite end to move out of engagement with said contact, said spring blade having a pair of substantially longitudinally extending slots formed therein, the portion of the blade between the slots forming a substantially longitudinal single arch extending out of the plane of the blade on one side thereof only and having its peak olfset to one side of its longitudinal midpoint, and said blade actuating member being adapted to engage said arch of the blade substantially at the peak thereof.

I References Cited in the file of this patent UNITED STATES PATENTS Lee June 17, Wilms Oct. 28, Dubilier June 2, Rath -1- Feb. 1, Riche Apr. 26, Eaton May 10, Kaminky Oct. 25, Ransome May 16, Charbonneau Oct. 24, Miller Oct. 30,

FOREIGN PATENTS Great Britain May 13, Great Britain Apr. 11, Great Britain Oct. 7, 

